The rate of IBD among children has doubled over the last decade. The study is the largest yet to suggest that the increased use of antibiotics may be at least partially to blame.

"We need to be judicious in our use of antibiotics," says researcher Matthew P. Kronman, MD, of Seattle Children's Hospital's division of infectious diseases. "Antibiotics should be used when needed. But too many children are still getting them for conditions like the common cold, where they do no good."

IBD Risk Higher in Antibiotic Users

Researchers followed more than a million children -- including close to 750 with IBD -- enrolled in a health registry in the U.K.

Those treated with antibiotics before their first birthday were more than five times more likely to develop IBD than those never treated with antibiotics.

Antibiotic exposure among older kids and teens was also linked to a raised risk for IBD, but the risk was not as great. And the more antibiotics prescribed during childhood and adolescence, the higher the risk.

The findings add to the evidence that antibiotic use may cause IBD, but they do not prove the link, says researcher Theoklis E. Zaoutis, MD, of the Children's Hospital of Philadelphia.

About 49 million antibiotic prescriptions are written for children each year in the U.S.

Based on their findings, the researchers estimated that 1,700 cases of IBD in children and teens are related to antibiotic use each year.

The study was published online today, and it appears in the October issue of Pediatrics.

Antibiotics Kill 'Good' Gut Bacteria

Antibiotics kill the bad bacteria that cause illness. But they also kill good bacteria in the body that help digestion.

IBD runs in families. Most experts believe that genes aren't the only trigger for the disease.

The study adds to the evidence that antibiotic use is one of these triggers, says Ilseung Cho, MD, of NYU Langone Medical Center.

Cho says the possible link reinforces the importance of prescribing antibiotics only when they are likely to be useful.

"Both physicians and parents are at fault for the overuse of antibiotics," he says. "Antibiotics are very beneficial drugs, but it is important to be prudent about how we use them."